1. Field of the Invention
The present invention relates to a method and apparatus for measuring the length of a multi-section telescopic boom.
2. Description of Related Art
Typical booms employed in the crane and aerial work platform industry have multiple sections, and the length of the boom varies with the extension and retraction of these boom sections. Because boom length affects load moment characteristics and other factors involved in lifting a load, the length of the boom is monitored.
One technique for measuring the length of a boom employs a cable and reel system. The reel is mounted to a base section of the boom. The cable is wound on the reel and anchored to a fly section of the boom. A rotary sensor or multi-turn potentiometer attached to the reel measures the length of the boom based on the sensed rotation of the reel. Several other techniques using potentiometers, rotary sensors, and optical rotary sensors are also known.
Unfortunately, boom length measuring techniques such as above-mentioned cable and reel system are very costly, cumbersome, and subject to malfunction (tangling of the cable, breaking of the cable, etc.)